JP2023160214A - Engine and saddle-riding type vehicle with the same - Google Patents

Abstract

To provide an engine which can be easily manufactured and can reduce noise, and a saddle-riding type vehicle equipped with the same.SOLUTION: A power unit 6 includes an engine 6A. The engine 6A has a crankshaft 61. The engine 6A further has a crankcase 62 which stores the crankshaft 61. A dynamic damper 200 is provided in the crankcase 62. The dynamic damper 200 includes a damper mass and a support member. The support member includes an elastic body and supports the damper mass in the crankcase. During operation of the engine 6A, flexural vibration is generated in the crankshaft 61. At that time, by elastic force of the elastic body, the damper mass vibrates on one straight line orthogonal to a center axis of the crankshaft 61 and parallel to a direction of the flexural vibration generated in the crankshaft 61.SELECTED DRAWING: Figure 2

Description

The present invention relates to an engine and a straddle-type vehicle equipped with the same.

2. Description of the Related Art Vibrations generated in the crankshaft during engine operation are transmitted to the crankcase, and noise is generated from the power unit and the like including the crankcase. In order to reduce such noise, Patent Document 1 proposes a crankshaft vibration prevention structure. In this anti-vibration structure, a dynamic damper is provided at the end of the crankshaft.

More specifically, in the engine described in Patent Document 1, a centrifugal oil strainer is attached to one end of a crankshaft that extends in one direction. A dynamic damper is attached to the oil strainer via a bowl-shaped mounting plate. The dynamic damper is composed of an annular elastic body and an annular damper weight, and has a structure in which the elastic body is baked into the mounting plate, thereby forming a unit with the mounting plate.

Japanese Patent Application Publication No. 2002-5235

Furthermore, in the dynamic damper described above, the vibration isolation performance of the damper weight is set in consideration of the fact that the stiffness of the crankcase differs depending on the direction. The vibration isolation performance of the damper weight is determined not only by the ratio of the mass of the damper weight to the mass of the crankshaft and the composition of the elastic body, but also by considering the arrangement of surrounding parts of the damper weight, the allowable size of the damper weight, etc. There is a need. Therefore, it is not easy to provide a dynamic damper on a crankshaft that rotates at high speed and to appropriately set its vibration damping performance. Therefore, it is not easy to produce the above engine.

Furthermore, in the engine described in Patent Document 1, vibrations reduced by the dynamic damper are transmitted from the crankshaft to the crankcase. The rigidity of a crankcase is determined by the shape and size of the crankcase. That is, the rigidities of multiple types of crankcases provided in multiple types of engines do not necessarily have common directional characteristics. Therefore, depending on the configuration of the crankcase, the vibrations reduced by the dynamic damper may be transmitted to the crankcase, which may cause excessive noise to be generated from the power unit or the like including the crankcase.

An object of the present invention is to provide an engine that is easy to manufacture and can reduce noise generation, and a straddle-type vehicle equipped with the same.

(1) An engine according to one aspect of the present invention includes a crankshaft, a crankcase that accommodates the crankshaft, and a dynamic damper provided in the crankcase, the dynamic damper having a damper mass, an elastic body, and a crankshaft. a support part that vibrably supports the damper mass on the crankcase so that the damper mass can vibrate by an elastic body on a straight line perpendicular to the central axis of the shaft and parallel to the direction of bending vibration generated in the crankshaft; including.

In this engine, a dynamic damper is provided in the crankcase. In this case, since there is no need to provide a dynamic damper on the crankshaft that rotates at high speed, the degree of freedom in designing and mounting the dynamic damper is improved, and the engine can be manufactured easily. Further, according to the above configuration, the damper mass of the dynamic damper vibrates on a straight line parallel to the direction of bending vibration of the crankshaft. As a result, vibrations transmitted to peripheral members of the crankshaft due to bending vibrations of the crankshaft are efficiently absorbed by the dynamic damper. Therefore, at least a portion of vibrations that cause noise generated from the power unit including the crankcase and its peripheral members are efficiently absorbed by the dynamic damper. As a result, an engine that is easy to manufacture and generates reduced noise is realized.

(2) The support part regulates the vibration direction of the damper mass so that the damper mass cannot vibrate on other straight lines that intersect with the first straight line, and the elastic force of the elastic body acts on the damper mass on the first straight line. As such, the damper mass may be supported so as to be able to vibrate on the crankcase.

According to the above configuration, the damper mass of the dynamic damper vibrates only on one straight line parallel to the direction of bending vibration of the crankshaft. As a result, vibrations that cause noise can be absorbed more efficiently.

(3) The support part has a first leaf spring part and a second leaf spring part as elastic bodies, and the first leaf spring part and the second leaf spring part are arranged in a direction parallel to one straight line. The first leaf spring part and the second leaf spring part may each be provided to connect the crankcase and the damper mass.

A leaf spring is thinner than other elastic bodies such as coil springs and rubber members. Therefore, according to the above configuration, the vibration direction of the damper mass relative to the crankcase can be regulated without requiring an excessive installation space.

(4) Each of the first leaf spring part and the second leaf spring part is formed into a flat plate shape having one face and the other face facing opposite to each other, and the crankshaft is arranged so that the one face and the other face are perpendicular to one straight line. It may be provided in the case. In this case, each of the first leaf spring part and the second leaf spring part is bent in a plane perpendicular to the central axis of the crankshaft, so that the damper mass vibrates on one straight line with a simple configuration.

(5) The crankcase has a mounting surface perpendicular to the central axis of the crankshaft, the support part has a first part and a second part attached to the mounting surface, and the crankshaft has a mounting surface perpendicular to the central axis of the crankshaft. When viewed in the direction along the central axis, the mounting surface is located in a region between a portion of the mounting surface to which the first portion of the support portion is attached and a portion of the mounting surface to which the second portion of the support portion is attached. Good too.

In this case, the damper mass can be arranged near the crankshaft when viewed in the direction along the central axis of the crankshaft. For example, the damper mass can be arranged to overlap the crankshaft. As a result, the center of gravity of the engine is less likely to become unstable due to vibrations of the damper mass, compared to a case where the damper mass is provided at a position far away from the crankshaft.

(6) The dynamic damper may further include a rubber member provided between the mounting surface of the crankcase and the damper mass. In this case, the rubber member absorbs the vibration of the damper mass caused by the elastic force of the first leaf spring part and the second leaf spring part. This suppresses the generation of noise caused by large vibrations of the damper mass.

(7) The engine may further include a bearing that supports the crankshaft within the crankcase, the crankcase may have a fixed part to which the bearing is fixed, and the dynamic damper may be attached to the fixed part.

A fixed part of the crankcase supports the crankshaft via a bearing. Therefore, vibrations from the crankshaft are easily transmitted to the fixed part. According to the above configuration, since the dynamic damper is attached to the fixed part, most of the vibrations transmitted from the crankshaft to the crankcase are efficiently absorbed by the dynamic damper.

(8) A straddle-type vehicle according to another aspect of the present invention includes a main body having a drive wheel, and the above engine that generates power for rotating the drive wheel.

The straddle-type vehicle is equipped with the above engine. This facilitates manufacturing of the saddle type vehicle. Furthermore, at least a portion of vibrations that cause noise generated from the power unit including the crankcase and its peripheral members are efficiently absorbed by the dynamic damper. As a result, a straddle-type vehicle that is easy to manufacture and generates less noise is realized.

Advantageous Effects of Invention According to the present invention, it becomes easy to manufacture an engine, and it is also possible to reduce noise generation in a power unit including the engine.

FIG. 1 is a right side view of a motorcycle according to an embodiment of the present invention. FIG. 2 is a side view of the power unit of FIG. 1 viewed from the right side of the motorcycle. FIG. 3 is a diagram for explaining bending vibration occurring in the crankshaft of FIG. 2. FIG. FIG. 3 is an exploded perspective view for explaining the configuration of the crankcase and dynamic damper in FIG. 2. FIG. 5 is a partially enlarged side view of the right case member of FIG. 4. FIG. It is a figure showing the inner surface of a damper mass. FIG. 5 is a front view of the support member of FIG. 4; FIG. 8 is a side view of the support member of FIG. 7 viewed in a first direction; FIG. 8 is a side view of the support member of FIG. 7 when viewed in a second direction. 3 is a sectional view taken along line AA of the power unit in FIG. 2. FIG. 3 is a sectional view taken along line BB of the power unit in FIG. 2. FIG. FIG. 3 is a schematic diagram for explaining the operation of the dynamic damper when absorbing vibrations transmitted from the crankshaft to the crankcase. FIG. 3 is a schematic diagram for explaining the operation of the dynamic damper when absorbing vibrations transmitted from the crankshaft to the crankcase.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An engine according to an embodiment of the present invention and a straddle-type vehicle equipped with the same will be described below with reference to the drawings. A motorcycle will be described as an example of a straddle-type vehicle.

<1> Schematic configuration of motorcycle FIG. 1 is a right side view of a motorcycle according to an embodiment of the present invention. In FIG. 1, a motorcycle 100 is shown standing vertically with respect to a road surface. A motorcycle 100 in FIG. 1 includes a body frame 1 made of metal. The vehicle body frame 1 includes a head pipe 11 and a plurality of frame members. In FIG. 1, two frame members 12 and 13 are shown among the plurality of frame members. The head pipe 11 is located at the front of the vehicle. The frame members 12 and 13 are provided so as to extend from the head pipe 11 toward the rear of the vehicle.

A front fork 2 is rotatably provided on the head pipe 11 with the center axis of the head pipe 11 as a reference. A front wheel 3 is rotatably supported at the lower end of the front fork 2. A handle 4 is provided at the upper end of the front fork 2.

Body frame 1 supports multiple components of motorcycle 100 including seat 5, power unit 6, and rear arm 7. The seat 5 is provided approximately at the upper center of the motorcycle 100 in the front-rear direction. The power unit 6 includes an engine 6A and is provided approximately at the lower center of the motorcycle 100 in the front-rear direction. In the left-right direction of the motorcycle 100, resin side covers are provided so as to sandwich the front half of the power unit 6 (engine 6A portion).

A rear arm 7 is provided so as to extend rearward from near the rear end of the power unit 6. The rear arm 7 is supported by the vehicle body frame 1 using a pivot shaft (not shown). A rear wheel 8 is rotatably supported at the rear end of the rear arm 7. The rear wheels 8 serve as driving wheels and are rotated by power generated from the engine 6A of the power unit 6.

When the engine 6A is in operation, noise may be generated from the motorcycle 100 due to the rotation of the crankshaft 61 included in the engine 6A. Therefore, the power unit 6 according to the present embodiment is provided with a dynamic damper 200 as a structure for reducing noise generated during engine operation. The mechanism of noise generation and the specific configuration and function of the dynamic damper 200 will be explained.

<2> Basic configuration of power unit 6 and bending vibration of crankshaft FIG. 2 is a side view of the power unit 6 in FIG. 1 viewed from the right side of the motorcycle 100. As mentioned above, power unit 6 includes engine 6A. Engine 6A has a cylinder head 63. The cylinder head 63 has a configuration in which two cylinders are arranged side by side in the left-right direction of the motorcycle 100. In FIG. 2, the outer shape of the cylinder head 63 is schematically shown with a dashed line.

Power unit 6 has a crankcase 62. The crankcase 62 according to this embodiment accommodates the crankshaft 61. The crankshaft 61 extends in the left-right direction of the motorcycle 100 within the crankcase 62.

Two pistons 64 are connected to the crankshaft 61 via two connecting rods 65, respectively. The two pistons 64 of the crankshaft 61 are each provided so as to be able to reciprocate within the two cylinders of the cylinder head 63. In FIG. 2, a right piston 64 and a right connecting rod 65 located inside the cylinder head 63 are shown in solid lines. Further, in FIG. 2, a virtual straight line passing through the central axis of the right cylinder of the cylinder head 63 is indicated by a two-dot chain line as the cylinder axis AS.

When the engine 6A is in operation, bending vibrations occur in the crankshaft 61. FIG. 3 is a diagram for explaining bending vibration generated in the crankshaft 61 of FIG. 2. As shown in FIG. In FIG. 3, the outline of the power unit 6 viewed from a position above the power unit 6 in the direction of the white arrow VP1 in FIG. 2 is shown by a dashed-dotted line. Further, in FIG. 3, a crankshaft 61, two pistons 64, and two connecting rods 65 provided inside the power unit 6 are shown by solid lines. Furthermore, in FIG. 3, a virtual straight line passing through the central axis of the crankshaft 61 is shown as a crankshaft line 61c by a two-dot chain line. Note that the direction of the white arrow VP1 in FIG. 2 is a direction perpendicular to the cylinder axis AS when the power unit 6 is viewed along the central axis (crank axis 61c) of the crankshaft 61.

When the crankshaft 61 rotates during operation of the engine 6A, the two pistons 64 connected to the crankshaft 61 reciprocate along the cylinder axis AS. In this case, a bending moment is generated on the crankshaft 61 at a predetermined period due to the pressure of the air-fuel mixture and the inertial force acting on each piston 64. As a result, as shown by the thick dotted line in FIG. 3, the crankshaft 61 is repeatedly bent in a direction in which its central portion approaches the cylinder head 63 and in a manner in which its central portion is bent in a direction away from the cylinder head 63. It will be done.

As a result, in this example, as shown by thick solid line arrows in FIGS. 2 and 3, the crankshaft 61 is aligned with the cylinder in a plane parallel to the two cylinder axes AS of the cylinder head 63 and the left-right direction of the motorcycle 100. It vibrates against the head 63. This vibration is the bending vibration of the crankshaft 61. Here, the direction of bending vibration of the crankshaft 61 is the direction in which the crankshaft 61 vibrates due to the bending moment generated in the crankshaft 61 during operation of the engine 6A. The direction of bending vibration of the crankshaft 61 in this example is parallel to the cylinder axis AS in a side view and perpendicular to the central axis (crank axis 61c) of the crankshaft 61 in a plan view.

When bending vibration of the crankshaft 61 having a specific frequency (for example, a frequency within a certain range including 800 Hz) is transmitted to a part of the crankcase 62, noise is generated by the vibration of the part of the crankcase 62. there's a possibility that. For example, if a portion of the outer surface of the crankcase 62 is repeatedly deformed into concave and convex shapes due to bending vibration of the crankshaft 61, relatively large noise is likely to be generated. Alternatively, when bending vibration of the crankshaft 61 having a specific frequency is transmitted to a portion of the frame members 12, 13 through the crankcase 62, noise is generated due to the vibration of the portion of the frame members 12, 13. there is a possibility. Furthermore, noise may be generated due to vibration of the side covers and the like attached to the frame members 12 and 13. Therefore, in the motorcycle 100 according to the present embodiment, a dynamic damper 200 is provided in the crankcase 62 in order to efficiently reduce vibrations transmitted from the crankshaft 61 to other members such as the crankcase 62.

<3> Crankcase 62 and dynamic damper 200
(1) Outline of configuration of crankcase 62 and dynamic damper 200 FIG. 4 is an exploded perspective view for explaining the configuration of crankcase 62 and dynamic damper 200 in FIG. 2. The crankcase 62 in FIG. 2 is composed of a plurality of case members. The dynamic damper 200 is attached to a case member facing right of the motorcycle 100 (hereinafter referred to as a right case member 62R) among the plurality of case members of the crankcase 62.

(2) Right case member 62R of crankcase 62
FIG. 5 is a partially enlarged side view of the right case member 62R of FIG. 4. FIG. As shown in FIG. 5, a bearing fixing portion 66 is provided on the right case member 62R. A bearing opening 67 is formed in the center of the bearing fixing portion 66 . The bearing opening 67 is a circular opening into which the right end of the crankshaft 61 can be inserted.

The bearing fixing part 66 has an annular bearing fitting part 69 at the inner edge of the bearing opening 67 and its surrounding area. The bearing fitting portion 69 is formed so that a bearing BR (FIG. 10), which will be described later, can be fitted from inside the crankcase 62. Further, the bearing fixing portion 66 has a substantially annular flat mounting surface 66s that surrounds the bearing opening 67 and the bearing fitting portion 69 and faces to the right of the motorcycle 100.

The bearing fixing portion 66 is formed with four screw holes h31 that open toward the right side of the motorcycle 100. The four screw holes h31 are distributed at equal angular intervals with the center of the bearing opening 67 as a reference so as to surround the bearing opening 67 and the bearing fitting part 69.

When the dynamic damper 200 is attached to the right case member 62R, a rubber member 230 of FIG. 4, which will be described later, is provided on the right-facing surface of the bearing fitting portion 69, as shown by the thick dotted line in FIG. Further, as shown by a thick dashed line in FIG. 5, a rubber member 240 shown in FIG. 4, which will be described later, is provided near the outer peripheral end of the mounting surface 66s. Furthermore, four screws sc2 shown in FIG. 4, which will be described later, are attached to the four screw holes h31.

(3) Configuration of each part of the dynamic damper 200 As shown in FIG. 4, the dynamic damper 200 includes a damper mass 210, a support member 220, and rubber members 230, 240. The rubber member 230 is an annular member such as an O-ring, and has an inner diameter and an outer diameter corresponding to the bearing fitting portion 69 of the right case member 62R. The rubber member 240 is a rubber annular member such as an O-ring, and has an inner diameter larger than that of the rubber member 230 and an outer diameter slightly smaller than the mounting surface 66s of the right case member 62R. The functions of the rubber member 230 and the rubber member 240 will be described later.

The damper mass 210 is a substantially disk-shaped member made of metal such as aluminum or stainless steel. The outer diameter of the damper mass 210 is equal to or slightly larger than the outer diameter of the rubber member 240. One surface and the other surface of the damper mass 210 that face each other are referred to as an outer surface 211 and an inner surface 212 of the damper mass 210, respectively.

The outer surface 211 of the damper mass 210 faces in the opposite direction (to the right) from the right case member 62R when the dynamic damper 200 is attached to the right case member 62R. Further, the outer surface 211 of the damper mass 210 is formed so as to gradually swell from the outer peripheral end of the damper mass 210 to the center thereof. On the other hand, the inner surface 212 of the damper mass 210 faces the mounting surface 66s of the right case member 62R when the dynamic damper 200 is attached to the right case member 62R.

FIG. 6 is a diagram showing the inner surface 212 of the damper mass 210. As shown in FIG. 6, in the inner surface 212 of the damper mass 210, a circular recess 212a is formed in the center. Further, an annular closed portion r1 is formed to surround the recessed portion 212a. The recess 212a has an inner diameter that is the same or approximately the same as the inner diameter of the bearing opening 67 of the right case member 62R in FIG.

The recess 212a is formed to be able to accommodate the right end portion of the crankshaft 61 protruding rightward from the right case member 62R, as will be described later, with the dynamic damper 200 attached to the right case member 62R. The annular closing part r1 has an annular groove into which a part of the rubber member 230 of FIG. 4 can be fitted, and has an inner diameter and an outer diameter corresponding to the bearing fitting part 69 of the right case member 62R of FIG. 5. When the dynamic damper 200 is attached to the right case member 62R, the rubber member 230 shown in FIG. 4 is provided so as to overlap the annular groove of the annular closing portion r1.

In the inner surface 212 of the damper mass 210, two grooves 212b are further formed to sandwich the recess 212a and the annular closing portion r1. Each of the two groove portions 212b extends linearly and is formed to be able to accommodate a portion of a later-described leaf spring portion 223 (FIG. 7) of the support member 220 in FIG. 4.

On the inner surface 212 of the damper mass 210, an annular closed portion r2 is formed in a region of a constant width including the outer peripheral end of the damper mass 210. The annular closing portion r2 has an annular groove into which a part of the rubber member 240 of FIG. 4 can be fitted. When the dynamic damper 200 is attached to the right case member 62R, the rubber member 240 shown in FIG. 4 is provided so as to overlap the annular groove of the annular closing portion r2.

Two supported surfaces 212c are formed in the inner surface 212 of the damper mass 210 in a region between the two grooves 212b and in a region excluding the annular blockage r2. In FIG. 6, the two supported surfaces 212c are indicated by dashed lines. One supported surface 212c is formed between the first groove portion 212b and a portion (arc-shaped portion) of the annular closed portion r2 at a position outside the recess portion 212a. The other supported surface 212c is formed between the other groove portion 212b and the other portion (arc-shaped portion) of the annular closed portion r2 at a position outside the recessed portion 212a. The two supported surfaces 212c are formed flat. When the dynamic damper 200 is attached to the right case member 62R, two damper mass connecting portions 222 (FIG. 7), which will be described later, of the support member 220 in FIG. 4 abut on the two supported surfaces 212c, respectively. In FIG. 6, a dot pattern is attached to a portion of the two supported surfaces 212c that is in contact with two damper mass connecting portions 222 (FIG. 7), which will be described later.

The damper mass 210 has eight through holes extending from the outer surface 211 to the inner surface 212. Among the eight through holes, four through holes h22 are distributed at equal angular intervals with respect to the center of the recess 212a so as to surround the recess 212a and the annular closure r1 in the region between the two grooves 212b. There is. These four through holes h22 respectively correspond to the four screw holes h31 (FIG. 5) of the right case member 62R, and are capable of inserting the entirety (including the head) of four screws sc2 (FIG. 4), which will be described later. have a common inner diameter.

Among the eight through holes, the remaining four through holes are four screw holes h21. The four screw holes h21 have a common inner diameter and a common inner peripheral surface shape, and are formed such that two screw holes h21 are located on each of the two supported surfaces 212c. These four screw holes h21 are used to screw the support member 220 shown in FIG. 4 to the inner surface 212 of the damper mass 210. The four screw holes h21 do not need to penetrate from the outer surface 211 to the inner surface 212 of the damper mass 210. The four screw holes h21 may be open only on the inner surface 212.

As described above, in the dynamic damper 200, the support member 220 is attached to the inner surface 212 of the damper mass 210. In this example, in the support member 220 of FIG. 4, the surface facing the inner surface 212 of the damper mass 210 is the front surface of the support member 220.

FIG. 7 is a front view of the support member 220 of FIG. 4. Here, regarding the support member 220, the direction of the arrow D1 in FIG. 7 when the support member 220 is viewed from the front is defined as a first direction D1, and the direction of the arrow D2 in FIG. 7 is defined as a second direction D2. . The first direction D1 and the second direction D2 are orthogonal to each other. Further, the direction of arrow D3 in FIG. 7, which is perpendicular to the first direction D1 and the second direction D2, is defined as a third direction D3. 8 is a side view of the support member 220 of FIG. 7 as viewed in the first direction D1, and FIG. 9 is a side view of the support member 220 of FIG. 7 as viewed in the second direction D2.

The support member 220 is composed of a single metal member, and is manufactured by bending, heat treating, etc. a sheet metal cut out into a predetermined shape. As shown in FIG. 7, the support member 220 has a substantially annular shape when viewed from the front, and is mainly composed of two case connection parts 221, two damper mass connection parts 222, and two leaf spring parts 223.

The two case connection parts 221 are formed to be lined up at intervals in the first direction D1 and to extend in the second direction D2 when the support member 220 is viewed from the front. Each case connection portion 221 has one surface and the other surface perpendicular to the third direction D3. Further, each case connection portion 221 is formed with two through holes h12. The four through holes h12 of the two case connection parts 221 correspond to the four screw holes h31 (FIG. 5) of the right case member 62R, respectively. The inner diameter of each through hole h12 is larger than the outer diameter of the shaft of a screw sc2 (FIG. 4), which will be described later, which is attached to each screw hole h31, and smaller than the outer diameter of the head of the screw sc2.

The two damper mass connecting portions 222 are formed so as to be lined up at intervals in the second direction D2 and to extend in the first direction D1 when the support member 220 is viewed from the front. Each damper mass connection portion 222 has one surface and the other surface perpendicular to the third direction D3. Further, each damper mass connecting portion 222 is formed with two through holes h11. The four through holes h11 of the two damper mass connecting parts 222 correspond to the four screw holes h21 (FIG. 6) of the damper mass 210, respectively. The inner diameter of each through hole h11 is larger than the outer diameter of the shaft of a screw sc1 (FIG. 4), which will be described later, which is attached to each screw hole h21, and smaller than the outer diameter of the head of the screw sc1.

The two leaf spring parts 223 are formed so as to respectively connect both ends of the two case connection parts 221 when the support member 220 is viewed from the front. Moreover, the two leaf spring parts 223 are formed to hold the two damper mass connection parts 222, respectively, at positions between the two case connection parts 221 in the first direction D1. The two damper mass connecting parts 222 are held at positions slightly shifted in the third direction D3 with respect to the two case connecting parts 221.

Further, each leaf spring portion 223 has a configuration bent at 90 degrees with respect to the case connecting portion 221 and the damper mass connecting portion 222, as shown in FIG. Therefore, each leaf spring portion 223 has one surface and the other surface perpendicular to the second direction D2.

As shown in FIG. 9, the leaf spring portion 223 has a first portion 223a, a second portion 223b, and a third portion 223c arranged in the first direction D1. The first portion 223a and the third portion 223c of the leaf spring portion 223 are directly connected to the two case connecting portions 221, respectively. Further, the second portion 223b of the leaf spring portion 223 is directly connected to one damper mass connecting portion 222 at a position between the first portion 223a and the third portion 223c in the first direction D1. ing. With such a configuration, for example, when a force in the second direction D2 is applied to the damper mass connecting portion 222 with the two case connecting portions 221 fixed, the second portion 223b of the leaf spring portion 223 It bends locally due to its elastic force. Thereby, the damper mass connecting portion 222 moves in the second direction D2 with respect to the two damper mass connecting portions 222.

(4) Attaching the dynamic damper 200 to the crankcase 62 FIG. 10 is a sectional view taken along the line AA of the power unit 6 in FIG. 2, and FIG. 11 is a sectional view taken along the line BB of the power unit 6 in FIG. The dynamic damper 200 is attached to the crankcase 62 as follows. It is assumed that, at the start of attachment of the dynamic damper 200 to the crankcase 62, the bearing BR is fitted into the bearing fitting portion 69 of the right case member 62R, as shown in FIGS. 10 and 11. Further, it is assumed that the vicinity of the right end portion of the crankshaft 61 is rotatably held by the right case member 62R by a bearing BR. Furthermore, it is assumed that the right end portion of the crankshaft 61 slightly protrudes outward (to the right) of the bearing fixing portion 66 through the bearing opening 67.

First, support is made so that the two leaf spring parts 223 in FIG. 7 are housed in the two groove parts 212b in FIG. 6, and the four through holes h11 in FIG. 7 overlap with the four screw holes h21 in FIG. A member 220 is positioned on the inner surface 212 of the damper mass 210. In this state, as shown by dotted arrows in FIG. 4, four screws sc1 are attached to the four screw holes h21 of the damper mass 210 through the four through holes h11 of the support member 220. As a result, as shown in FIG. 10, the two damper mass connecting portions 222 (FIG. 7) of the support member 220 are connected to the two supported surfaces 212c (FIG. 6) of the damper mass 210. In this case, the two case connection parts 221 (FIG. 7) of the support member 220 are spaced apart from the inner surface 212 of the damper mass 210 so that the four through holes h12 face the four through holes h22 of the damper mass 210, respectively. Positioned.

Next, the rubber member 230 is positioned on the right-facing surface of the bearing fitting portion 69 of the right case member 62R. Furthermore, a rubber member 240 is positioned near the outer peripheral end of the mounting surface 66s of the right case member 62R. In this state, the damper mass 210 is positioned on the mounting surface 66s of the right case member 62R so that the rubber member 230 and the rubber member 240 overlap the annular closure part r1 and the annular closure part r2, respectively. Further, the damper mass 210 is positioned on the mounting surface 66s of the right case member 62R so that the four through holes h22 (FIG. 6) of the damper mass 210 overlap with the four screw holes h31 (FIG. 5) of the right case member 62R. .

Thereafter, as shown by the thick dashed-dotted arrows in FIG. Each can be installed. As a result, as shown in FIG. 11, the two case connecting portions 221 (FIG. 7) of the support member 220 are connected to the mounting surface 66s (FIG. 5) of the right case member 62R. In this way, the dynamic damper 200 is attached to the bearing fixing portion 66 of the right case member 62R.

With the dynamic damper 200 attached to the crankcase 62, the right end portion of the crankshaft 61 protruding from the bearing opening 67 of the bearing fixing portion 66 is accommodated in the recess 212a of the damper mass 210. A rubber member 230 is provided between the annular closing portion r1 of the damper mass 210 and the bearing fitting portion 69 of the right case member 62R. As a result, the space around the right end of the crankshaft 61 surrounded by the damper mass 210 and the right case member 62R is closed off by the rubber member 230 from the space outside the power unit 6. Further, a rubber member 240 is further provided between the damper mass 210 and the mounting surface 66s of the right case member 62R so as to surround the rubber member 230. With this configuration, in the power unit 6 of this example, oil supplied to the right end of the crankshaft 61 is prevented from leaking from inside the crankcase 62 through the attachment portion of the dynamic damper 200.

(5) Operation of dynamic damper 200 The dynamic damper 200 described above absorbs at least a portion of the vibrations transmitted from the crankshaft 61 to the crankcase 62 by being attached to the crankcase 62. The operation of the dynamic damper 200 at this time will be explained.

12 and 13 are schematic diagrams for explaining the operation of the dynamic damper 200 when absorbing vibrations transmitted from the crankshaft 61 to the crankcase 62. FIG. 12 shows a schematic diagram of the dynamic damper 200 viewed from a position facing the outer surface 211 of the damper mass 210. FIG. 13 shows a cross-sectional view through the center of the dynamic damper 200 of FIG. 12. In FIGS. 12 and 13, illustration of some components of the dynamic damper 200 is omitted so that the operation of the dynamic damper 200 can be easily understood. Furthermore, the scale of the dimensions of each part of the dynamic damper 200 has been changed.

As shown by the dashed line in FIGS. 12 and 13, one virtual straight line VL1 is defined that is parallel to the direction of bending vibration of the crankshaft 61 and orthogonal to the crank axis 61c. In this case, the two leaf spring parts 223 of the support member 220 are provided so that one surface and the other surface thereof are orthogonal to the virtual straight line VL1. Thereby, the deformable direction of each leaf spring portion 223 is limited to a plane approximately parallel to the crank axis 61c and the virtual straight line VL1. Furthermore, as shown in FIG. 12, the support member 220 is attached to the mounting surface 66s so that the two damper mass connecting portions 222 are lined up at intervals on the virtual straight line VL1 when viewed in the direction along the crank axis 61c. There is.

In these cases, the movable direction of the damper mass 210 is restricted by the two damper mass connecting portions 222 and the two leaf spring portions 223 to the direction along the virtual straight line VL1. Therefore, when bending vibration occurs in the crankshaft 61, the damper mass 210 vibrates on the virtual straight line VL1, as shown by the thick solid arrow in FIGS. 12 and 13, and vibrates in a direction deviating from the virtual straight line VL1. do not. Therefore, at least a portion of the bending vibration generated in the crankshaft 61 is efficiently absorbed by the vibration of the damper mass 210.

Further, the support member 220 is attached to the mounting surface 66s so that the crankshaft 61 is located between the two damper mass connecting portions 222 when viewed in the direction along the crank axis 61c. Further, the support member 220 is attached to the mounting surface 66s so that the crankshaft 61 is located between the two case connecting parts 221 when viewed in the direction along the crank axis 61c.

In such a configuration, the damper mass 210 overlaps at least the crankshaft 61 on the virtual straight line VL1 when viewed in the direction along the crankshaft line 61c. As a result, the center of gravity of the engine 6A is less likely to become unstable due to vibrations of the damper mass 210, compared to a case where the damper mass 210 is provided at a position far away from the crankshaft 61 when viewed in the direction along the crank axis 61c. .

The frequency of vibration that can be damped by the dynamic damper 200 is a natural value, and the natural value is determined mainly based on the weight of the damper mass 210 and the elastic force of the leaf spring portion 223. Therefore, it is preferable that the weight of the damper mass 210 and the elastic force of the leaf spring section 223 are determined in advance so that the frequency of vibration that can be damped by the dynamic damper 200 matches a specific frequency band. The specific frequency band is a frequency band that greatly contributes to higher level noise among the noise generated from the motorcycle 100 when the engine 6A is operating. Setting the weight of the damper mass 210 and the elastic force of the leaf spring portion 223 and selecting a specific frequency band are preferably performed by, for example, experiments or simulations.

<4> Effects (1) In the power unit 6 according to the present embodiment, the dynamic damper 200 is provided in the crankcase 62. In this case, since it is not necessary to directly provide the dynamic damper 200 on the crankshaft 61 that rotates at high speed, the degree of freedom in designing and mounting the dynamic damper 200 is improved, and the production of the power unit 6 is facilitated. Further, according to the above configuration, the damper mass 210 of the dynamic damper 200 vibrates on the virtual straight line VL1 parallel to the direction of bending vibration of the crankshaft 61. As a result, vibrations transmitted to peripheral members of the crankshaft 61 due to bending vibrations of the crankshaft 61 are efficiently absorbed by the dynamic damper 200. Therefore, vibration of the crankcase 62 and its surrounding members due to bending vibration of the crankshaft 61 is efficiently reduced. Alternatively, vibration of at least a portion of the frame members 12 and 13 due to bending vibration of the crankshaft 61 is efficiently reduced. As a result, a power unit 6 that is easy to manufacture and that generates less noise due to bending vibration of the crankshaft 61 is realized.

(2) The dynamic damper 200 according to the above embodiment includes rubber members 230 and 240 provided between the mounting surface 66s of the right case member 62R and the damper mass 210. In this case, the rubber members 230 and 240 function as a closing member that prevents the oil in the crankcase 62 from leaking from the attachment portion of the dynamic damper 200, as described above. Further, the rubber members 230 and 240 absorb part of the vibration of the damper mass 210 when bending vibration occurs in the crankshaft 61. Thereby, generation of noise due to excessive vibration of the damper mass 210 is suppressed.

<5> Example The present inventors produced a power unit having the same configuration as the power unit 6 according to the above embodiment as a power unit of an example. Furthermore, the present inventors produced a power unit as a comparative example, which has the same configuration as the power unit 6 according to the embodiment described above, except that it does not include the dynamic damper 200 described above.

Furthermore, the present inventors operated the engines of the power unit of the example and the power unit of the comparative example under predetermined common conditions, and measured the magnitude of noise having a wavelength in a specific region that was generated during the operation. . As a result, it was confirmed that the level of noise generated from the power unit of the example was lower than the level of noise generated from the power unit of the example.

<6> Other Embodiments (1) In the power unit 6 according to the above embodiment, the dynamic damper 200 is provided in a portion of the right case member 62R that covers the right end of the crankshaft 61. but not limited to. The dynamic damper 200 may be provided in a portion of the right case member 62R that is spaced apart from the crankshaft 61. For example, the dynamic damper 200 may be provided at any of the front end, upper end, lower end, and rear end of the crankcase 62. Even in these cases, the same effects as in the above embodiments can be obtained by limiting the vibration direction of damper mass 210 to the direction of bending vibration of crankshaft 61.

(2) In the power unit 6 according to the embodiment described above, one dynamic damper 200 is provided in the engine 6A, but the present invention is not limited to this. The power unit 6 is not limited to one dynamic damper 200, but may be provided with two or three dynamic dampers 200. For example, in the power unit 6 described above, a new dynamic damper 200 may be provided on the left side of the crankcase 62.

(3) In the dynamic damper 200 according to the above embodiment, the two leaf spring portions 223 of the support member 220 are aligned in the direction of bending vibration of the crankshaft 61 when viewed from the side of the motorcycle 100. Thereby, the vibration direction of the damper mass 210 is regulated so as to be along one imaginary straight line VL1 parallel to the direction of bending vibration of the crankshaft 61. However, in the present invention, the configuration for regulating the vibration direction of damper mass 210 is not limited to the above example. The dynamic damper 200 may have the following configuration instead of the support member 220 described above.

For example, the right case member 62R is provided with a guide shaft extending along one virtual straight line VL1. Further, a damper mass 210 is provided on the guide shaft so as to be movable along the direction of the guide shaft. Furthermore, an elastic body (for example, a coil spring) is provided that allows the damper mass 210 to move within a certain range along the guide shaft and supports the damper mass 210 on a part of the guide shaft or a part of the right case member 62R. . Even when such a configuration is provided in the crankcase 62, the vibration direction of the damper mass 210 can be restricted to the direction of the bending vibration of the crankshaft 61. Thereby, effects similar to those of the above embodiment can be obtained.

(4) Although the dynamic damper 200 according to the above embodiment has two rubber members 230 and 240, the present invention is not limited thereto. For example, if oil inside the crankcase 62 is prevented from leaking to the outside of the power unit 6 by a configuration other than the dynamic damper 200, the dynamic damper 200 may not include at least one of the two rubber members 230 and 240. Good too.

(5) Some power units for straddle-type vehicles have a configuration in which, for example, a crankshaft and a plurality of power transmission members attached to the crankshaft are individually housed in a plurality of cases that are integrally connected to each other. be. For example, there is a configuration in which a case housing a crankshaft and a case housing a belt-type continuously variable transmission (CVT) attached to the crankshaft are integrally connected. Alternatively, there is a configuration in which a case housing a crankshaft and a case housing a drive shaft attached to the crankshaft are integrally connected. Alternatively, there is a configuration in which a case accommodating a crankshaft and a case accommodating a clutch attached to the crankshaft are integrally connected. In such a configuration, a plurality of integrally connected cases may be regarded as the crankcase according to the present invention, and at least one of the plurality of cases may be provided with the dynamic damper according to the above embodiment. good. Even in this case, since the plurality of cases constituting the power unit are integrally connected, the same effects as in the above embodiment can be obtained.

(6) In the dynamic damper 200 according to the above embodiment, the support member 220 that supports the damper mass 210 on the right case member 62R is composed of a single member including two leaf spring parts 223. It is not limited to this. In a configuration in which the damper mass 210 is supported by the right case member 62R, the support member 220 may be separated so that the two leaf spring portions 223 are spaced apart from each other.

That is, the dynamic damper 200 may have two support members each made of two leaf spring members instead of the support member 220 described above. In this case, a portion of the damper mass 210 is supported by a portion of the right case member 62R, for example, by one leaf spring member. Further, the other portion of the damper mass 210 is supported by the other portion of the right case member 62R by the other leaf spring member. Further, the arrangement and posture of the two leaf spring members are adjusted so that the direction of vibration of the damper mass 210 is parallel to the direction of bending vibration of the crankshaft 61. Thereby, effects similar to those of the above embodiment can be obtained.

(7) In the dynamic damper 200 according to the above embodiment, a weight adjustment member for adjusting the weight of the damper mass 210 may be attached to the damper mass 210. In this case, the damper mass 210 is formed with a screw hole for a heavy member to which, for example, a plurality of types of heavy members can be screwed. Thereby, a weight member having a desired weight can be easily attached to and detached from the damper mass 210.

(8) Although the engine 6A according to the embodiment described above includes the cylinder head 63 in which two cylinders are arranged side by side in the left-right direction of the motorcycle 100, the present invention is not limited thereto. The engine 6A may have a configuration that includes only one cylinder, or may have a configuration that includes three or four or more cylinders. Further, the engine 6A is not limited to the above example, and may have a configuration in which one or three or more cylinders are arranged in a row in the left-right direction of the motorcycle 100. Alternatively, the engine 6A may have a configuration in which one or more cylinders are arranged in a line in the longitudinal direction of the motorcycle 100. Further, the engine 6A may have a configuration in which four cylinders are arranged in a matrix in a plan view, or a configuration in which a plurality of cylinders are arranged in a V-shape in a side view. You may.

The direction of bending vibration generated in the crankshaft 61 varies depending on the configuration of the engine 6A, but can be derived from predetermined dimensions of each part. Therefore, even if the number and arrangement of cylinders in the engine 6A are different from those in the above embodiment, the dynamic damper 200 can be attached to the crankcase 62 so that the damper mass 210 vibrates in the direction of bending vibration. can.

(9) Although the above embodiment is an example in which the present invention is applied to a motorcycle, the present invention is not limited to this, and can be applied to other saddles such as a four-wheeled motor vehicle, a three-wheeled motor vehicle, or an ATV (All Terrain Vehicle). The present invention may also be applied to riding vehicles.

<7> Correspondence between each part of the embodiment and each component of the claim Hereinafter, an example of the correspondence between each component of the claim and each element of the embodiment will be described. Not limited. Various other elements having the configuration or function described in the claims can also be used as each component in the claims.

In the above embodiment, the crankshaft 61 is an example of a crankshaft, the crankcase 62 is an example of a crankcase, the dynamic damper 200 is an example of a dynamic damper, the damper mass 210 is an example of a damper mass, The virtual straight line VL1 is an example of one straight line, the support member 220 is an example of a support member, and the power unit 6 and the engine 6A are examples of an engine.

Further, the crank axis 61c is an example of the central axis of the crankshaft, the mounting surface 66s of the right case member 62R is an example of the mounting surface, and one of the leaf spring parts 223 of the two leaf spring parts 223 of the support member 220 is is an example of the first leaf spring part, and the other leaf spring part 223 of the two leaf spring parts 223 of the support member 220 is an example of the second leaf spring part, and the two cases of the support member 220 are connected. One of the case connection parts 221 of the parts 221 is an example of the first part, and the other case connection part 221 of the two case connection parts 221 of the support member 220 is an example of the second part.

Further, the one surface and the other surface of each of the two leaf spring parts 223 of the support member 220 are examples of the one face and the other face of each of the first leaf spring part and the second leaf spring part facing opposite to each other, and the rubber The members 230 and 240 are examples of rubber members, the bearing BR is an example of a bearing, the bearing fixing part 66 of the right case member 62R is an example of a fixing part, the rear wheel 8 is an example of a driving wheel, and the power unit The entire motorcycle 100 except for parts 6 is an example of a main body, and the motorcycle 100 is an example of a straddle-type vehicle.

DESCRIPTION OF SYMBOLS 1...Body frame, 2...Front fork, 3...Front wheel, 4...Handle, 5...Seat, 6...Power unit, 6A...Engine, 7...Rear arm, 8...Rear wheel, 11...Head pipe, 12, 13...Frame member , 61... Crankshaft, 61c... Crank axis, 62... Crank case, 62R... Right case member, 63... Cylinder head, 64... Piston, 65... Connecting rod, 66... Bearing fixing part, 66s... Mounting surface, 67... Bearing opening Part, 69... Bearing fitting part, 100... Motorcycle, 200... Dynamic damper, 210... Damper mass, 211... Outer surface, 212... Inner surface, 212a... Recessed part, 212b... Groove, 212c... Supported surface, 220... Supporting member, 221 ...Case connection part, 222...Damper mass connection part, 223...Leaf spring part, 223a...First part, 223b...Second part, 223c...Third part, 230, 240...Rubber member, AS...Cylinder axis, BR... Bearing, D1... First direction, D2... Second direction, D3... Third direction, VL1... Virtual straight line, h11, h12, h22... Through hole, h21, h31... Screw hole, r1, r2... Annular closure part, sc1, sc2...screw

Claims (8)

crankshaft and
a crankcase that accommodates the crankshaft;
and a dynamic damper provided in the crankcase,
The dynamic damper is
Dampamas and
The damper mass has an elastic body and is configured such that the damper mass can vibrate by the elastic body on a straight line perpendicular to the central axis of the crankshaft and parallel to the direction of bending vibration generated in the crankshaft. and a support portion that vibrably supports the crankcase. The supporting portion regulates the vibration direction of the damper mass so that the damper mass cannot vibrate on another straight line that intersects with the one straight line, and the elastic force of the elastic body is arranged so that the elastic force of the elastic body The engine according to claim 1 , wherein the damper mass is vibrably supported on the crankcase so as to act on the damper mass. The support part has a first leaf spring part and a second leaf spring part as the elastic body,
The first leaf spring part and the second leaf spring part are provided in the crankcase so as to be lined up at intervals in a direction parallel to the one straight line,
3. The engine according to claim 1, wherein each of the first leaf spring part and the second leaf spring part is provided to connect the crankcase and the damper mass. Each of the first leaf spring part and the second leaf spring part is formed into a flat plate shape having one face and the other face facing opposite to each other, and the one face and the other face are perpendicular to the one straight line. The engine according to claim 3, wherein the engine is provided in the crankcase. The crankcase has a mounting surface perpendicular to the central axis of the crankshaft,
The support part has a first part and a second part attached to the mounting surface,
The crankshaft includes a portion of the mounting surface to which the first portion of the support portion is attached, and a portion of the mounting surface to which the first portion of the support portion is attached. Engine according to any one of claims 1 to 4, located in the area between the part and the part to which it is attached. The engine according to any one of claims 1 to 5, wherein the dynamic damper further includes a rubber member provided between the mounting surface of the crankcase and the damper mass. further comprising a bearing that supports the crankshaft within the crankcase,
The crankcase has a fixing part to which the bearing is fixed,
The engine according to any one of claims 1 to 6, wherein the dynamic damper is attached to the fixed part. a main body having a drive wheel;
A straddle-type vehicle, comprising the engine according to any one of claims 1 to 7, which generates power for rotating the drive wheels.

Images